Liquid phase chemical reactions requiring heterogeneous catalysis can be performed continuously in multi-contact reactors. For example,the patent application WO 92/10486 describes a method for the preparation of 5-hydroxymethyl furfural (HMF) by means of heterogeneous catalysis in liquid/liquid extraction reactors which may be pulsed columns.
The pulsed columns are vertical extraction or separation columns with horizontal plates of the disk and collar and/or collar and basket types and in which at least one solid phase is generally circulated downwards by gravity and at least one liquid phase is circulated in co-flow or in counter-flow. A pulsed column is equipped with a device capable of maintaining pulsations of the liquid phases within the column through an appropriate lining. It is known that the amplitude and the frequency of the pulsations can be regulated as a function of the respective residence times desired for the different phases in the column.
Thus, the document "Pulsed perforated-plate columns", D. H. Logsdail, M. J. Slaten, Handbook of Solvent Extraction, Teh C. Lo, Malcolm H. I. Baird, Carl Hanson, Krieger Publishing Company, Malabar, Fla., 1991, 11-2, p. 335-372, describes the general principles of pulsed columns.